U.S. patent application number 13/572728 was filed with the patent office on 2012-12-06 for polymer-based solid electrolytes and preparation methods thereof.
This patent application is currently assigned to TAIWAN TEXTILE RESEARCH INSTITUTE. Invention is credited to Yan-Ru Chen, Kuo-Feng Chiu, Wen-Hsien Ho, Shih-Hsuan Su, Chung-Bo Tsai.
Application Number | 20120308899 13/572728 |
Document ID | / |
Family ID | 47261918 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120308899 |
Kind Code |
A1 |
Tsai; Chung-Bo ; et
al. |
December 6, 2012 |
Polymer-Based Solid Electrolytes and Preparation Methods
Thereof
Abstract
SPEEK solid electrolytes and preparation methods thereof are
provided. The SPEEK solid electrolyte comprises sulfonated
polyetheretherketone (SPEEK), an electrolyte, and a solvent. The
electrolyte is a lithium salt.
Inventors: |
Tsai; Chung-Bo; (New Taipei
City, TW) ; Chen; Yan-Ru; ( New Taipei City, TW)
; Ho; Wen-Hsien; (New Taipei City, TW) ; Chiu;
Kuo-Feng; ( New Taipei City, TW) ; Su;
Shih-Hsuan; (New Taipei City, TW) |
Assignee: |
TAIWAN TEXTILE RESEARCH
INSTITUTE
New Taipei City
TW
|
Family ID: |
47261918 |
Appl. No.: |
13/572728 |
Filed: |
August 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13397883 |
Feb 16, 2012 |
|
|
|
13572728 |
|
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|
Current U.S.
Class: |
429/307 ;
429/306; 429/314; 429/317 |
Current CPC
Class: |
Y02E 60/10 20130101;
H01M 2300/0082 20130101; C08J 5/2256 20130101; H01M 10/0565
20130101 |
Class at
Publication: |
429/307 ;
429/306; 429/314; 429/317 |
International
Class: |
H01M 10/056 20100101
H01M010/056 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2011 |
TW |
100105123 |
Claims
1. A SPEEK solid electrolyte having conductivity's thermal change
rate smaller than 80% and capacitance's thermal change rate smaller
than 110%, the SPEEK solid electrolyte comprising: sulfonated
polyetheretherketone (SPEEK); a first lithium salt distributed in
the SPEEK, wherein a concentration of the first lithium salt is at
most 9.4 mmol/g; and a polar aprotic solvent, wherein a content of
the solvent is less than 40 wt %.
2. The SPEEK solid electrolyte of claim 1, wherein a molecular
weight of the SPEEK is 10,000-50,000 Da.
3. The SPEEK solid electrolyte of claim 1, wherein the first
lithium salt is LiClO.sub.4, LiBF.sub.4, LiPF.sub.6, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.3).sub.2, LiBr, or any
combinations thereof.
4. The SPEEK solid electrolyte of claim 1, wherein the polar
aprotic solvent comprises dimethyl sulfoxide, N-methyl
pyrrolidinone, Dimethylformamide, Dimethylacetamide, or any
combinations thereof.
5. The SPEEK solid electrolyte of claim 1, further comprising a
lithium salt solution, which adsorbs on or enters into the SPEEK
solid electrolyte by immersing the SPEEK solid electrolyte in the
lithium salt solution.
6. The SPEEK solid electrolyte of claim 5, wherein a second lithium
salt of the lithium salt solution is LiOH, LiNO.sub.3,
Li.sub.2SO.sub.4, LiClO.sub.4, LiCF.sub.3SO.sub.3,
LiN(CF.sub.3SO.sub.3).sub.2, or any combinations thereof.
7. The SPEEK solid electrolyte of claim 5, wherein a solvent of the
lithium salt solution is ethylene carbonate, ethyl methyl
carbonate, dimethyl carbonate, or propylene carbonate.
8. A flexible lithium battery, comprising: a substrate; two
SPEEK-solid electrolyte layers on opposite surfaces of the
substrate, composition of the two SPEEK-solid electrolyte layers
comprising: sulfonated polyetheretherketone (SPEEK); a first
lithium salt distributed in the SPEEK, and a content of the first
lithium salt to the SPEEK being at most 9.4 mmol/g; and a polar
aprotic solvent, wherein a content of the solvent is less than 40
wt %; and two electrode layers on two exposed surfaces of the two
SPEEK-solid electrolyte layers.
9. A preparation method of a SPEEK solid electrolyte, comprising:
preparing a sulfonated polyetheretherketone (SPEEK) solution by
dissolving SPEEK in a polar aprotic solvent; dissolving a first
lithium salt in the SPEEK solution to form a SPEEK electrolyte
solution; coating the SPEEK electrolyte solution on a substrate;
and drying the SPEEK electrolyte solution to form a SPEEK solid
electrolyte layer on the substrate.
10. The preparation method of claim 9, wherein a molecular weight
of the SPEEK is 10,000-50,000 Da.
11. The preparation method of claim 9, wherein the polar aprotic
solvent comprises dimethyl sulfoxide, N-methyl pyrrolidinone,
dimethylformamide, dimethylacetamide, or any combinations
thereof.
12. The preparation method of claim 9, wherein the first lithium
salt is LiClO.sub.4, LiBF.sub.4, LiPF.sub.6, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.3).sub.2, LiBr, or any
combinations thereof.
13. The preparation method of claim 9, wherein a weight ratio of
the first lithium salt to the SPEEK is at most 2 in the SPEEK
electrolyte solution.
14. The preparation method of claim 9, wherein the SPEEK
electrolyte solution is dried at a temperature of about
60-120.degree. C. for at most 72 hours.
15. The preparation method of claim 9, wherein a solvent content of
the SPEEK solid electrolyte is smaller than 40 wt %.
16. The preparation method of claim 9, further comprising immersing
the SPEEK solid electrolyte layer in a lithium salt solution for
about 1-60 sec after the drying step.
17. The preparation method of claim 16, wherein a second lithium
salt of the lithium salt solution is LiOH LiNO.sub.3,
Li.sub.2SO.sub.4, LiClO.sub.4, LiCF.sub.3SO.sub.3, or
LiN(CF.sub.3SO.sub.3).sub.2, or any combinations thereof.
18. The preparation method of claim 16, wherein the concentration
of the second lithium salt in the lithium salt solution is at most
10 M.
19. The preparation method of claim 16, wherein a solvent of the
lithium salt solution is ethylene carbonate, ethyl methyl
carbonate, dimethyl carbonate, or propylene carbonate.
20. The preparation method of claim 9, further comprising forming
two electrode layers respectively on opposite outer surfaces of the
SPEEK solid electrolyte layer on the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation-in-part
application of U.S. application Ser. No. 13/397,883, filed Feb. 16,
2012, which claims priority to Taiwanese Application Serial Number
100105123, filed Feb. 16, 2011. The entire disclosures of all the
above applications are hereby incorporated by reference herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The disclosure relates to an electrolyte and a preparation
method thereof. More particularly, the disclosure relates to a
solid electrolyte and a preparation method thereof.
[0004] 2. Description of Related Art
[0005] Lithium secondary (rechargeable) batteries (abbreviated as
lithium batteries below) have advantages of high working potential,
high energy potential, light weight, and long life. Therefore, the
lithium batteries have been widely applied on consumer electronics
products and some high power products.
[0006] The electrolyte used in the lithium batteries can be divided
into liquid electrolyte and solid electrolyte. Although the liquid
electrolyte has higher ionic conductivity, the electrolyte is
easily leaked, and thus a more complicated package is needed.
Therefore, it is difficult to reduce the size of the lithium
batteries using liquid electrolyte.
[0007] Comparing with the liquid electrolyte, the lithium batteries
using solid electrolyte (also called as solid thin film batteries)
do not need to worry about the leakage problem, and thus have
higher safety. Furthermore, since the thickness of the solid thin
film batteries is only 1-20 .mu.m, the solid thin film batteries
can be made into any sizes and shapes to meet various requirements.
Moreover, the solid thin film batteries have high power density,
can be charged and discharged for thousands times and in a
high-temperature environment. Since the solid thin film batteries
have the features above, the solid thin film batteries have been
applied in products, such as IC card, flexible electronic devices,
and biomedical applications; those need thin flexible power
supply.
[0008] In the research of the solid electrolyte, the main goals
still include increasing the energy density, the number of charge
and discharge cycles, the mechanical strength, reliability, the
thermal stability of the solid thin film batteries.
SUMMARY
[0009] Accordingly, one aspect of this invention is to provide a
polymer-based solid electrolyte that has a small thermal change
rate of conductivity and capacitance to provide a stable
conductivity and capacitance over a wide temperature range.
[0010] Accordingly, a SPEEK solid electrolyte is provided. The
SPEEK solid electrolyte comprises a lithium salt, sulfonated
polyetheretherketone (SPEEK), and a polar aprotic solvent.
[0011] According to an embodiment, the lithium salt can be
LiClO.sub.4, LiBF.sub.4, LiPF.sub.6, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.3).sub.2, LiBr, or any
combinations thereof.
[0012] According to another embodiment, the SPEEK has a molecular
weight of about 10,000-50,000 Da.
[0013] According to yet another embodiment, the polar aprotic
solvent comprises dimethyl sulfoxide, N-methyl pyrrolidinone,
dimethylformamide, dimethylacetamide, or any combinations
thereof.
[0014] According to yet another embodiment, a weight ratio of the
lithium salt to the SPEEK is at most 2.
[0015] According to yet another embodiment, the polar aprotic
solvent comprises dimethyl sulfoxide, N-methyl pyrrolidinone,
Dimethylformamide, Dimethylacetamide, or any combinations
thereof.
[0016] According to yet another embodiment, the content of the
polar aprotic solvent is at most 40 wt %.
[0017] According to yet another embodiment, the SPEEK solid
electrolyte further comprises a lithium salt solution, which
adsorbs on or enters into the SPEEK solid electrolyte by immersing
the SPEEK solid electrolyte in the lithium salt solution.
[0018] According to yet another embodiment, the lithium salt of the
lithium salt solution above is LiOH, LiNO.sub.3, Li.sub.2SO.sub.4,
LiClO.sub.4, LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.3).sub.2, or
any combinations thereof.
[0019] According to yet another embodiment, the solvent of the
lithium salt solution is ethylene carbonate, ethyl methyl
carbonate, dimethyl carbonate, or propylene carbonate.
[0020] In another aspect, this invention also provides a method of
preparing the various SPEEK solid electrolytes above.
[0021] In this preparation method, a SPEEK solution is prepared by
dissolving sulfonated polyetheretherketone (SPEEK) in a polar
aprotic solvent. Then, a lithium salt is dissolved in the SPEEK
solution to form a SPEEK electrolyte solution. Next, the SPEEK
electrolyte solution is coated on a substrate and then dried to
form a SPEEK solid electrolyte layer on the substrate.
[0022] According to an embodiment, the SPEEK electrolyte solution
is dried at a temperature of about 60-120.degree. C. for at most 72
hours.
[0023] According to another embodiment, the SPEEK solid electrolyte
layer can further immersed in the lithium salt solution above for
about 1-60 sec after the drying step to reduce the charge transfer
resistance between the solid electrolyte and a contacting
electrode, but also increase the mobility of ions in solid
electrolyte.
[0024] The foregoing presents a simplified summary of the
disclosure in order to provide a basic understanding to the reader.
This summary is not an extensive overview of the disclosure and it
does not identify key/critical elements of the present invention or
delineate the scope of the present invention. Its sole purpose is
to present some concepts disclosed herein in a simplified form as a
prelude to the more detailed description that is presented
later.
[0025] Many of the attendant features will be more readily
appreciated as the same becomes better understood by reference to
the following detailed description considered in connection with
the accompanying drawings.
DETAILED DESCRIPTION
[0026] In the following detailed description, for purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of the disclosed embodiments. It
will be apparent, however, that one or more embodiments may be
practiced without these specific details. In other instances,
well-known structures and devices are schematically shown in order
to simplify the drawing.
SPEEK Solid Electrolyte
[0027] In one aspect, this invention provides a polymer-based solid
electrolyte that has a small thermal change rate of conductivity
and capacitance to provide a stable conductivity and capacitance
over a wide temperature range. Accordingly, a SPEEK solid
electrolyte having a small thermal change rate of conductivity and
capacitance over a temperature range of 25-80.degree. C. is
provided below. The thermal change rate of the conductivity can be
smaller than 80%, and the thermal change rate of the capacitance
can be smaller than 110%. The SPEEK solid electrolyte comprises a
lithium salt, sulfonated polyetheretherketone (SPEEK), and a polar
aprotic solvent.
[0028] According to an embodiment, the lithium salt above can be a
lithium salt with lower lattice energy, such as LiClO.sub.4,
LiBF.sub.4, LiPF.sub.6, LiAsF.sub.6, LiCF.sub.3SO.sub.3,
LiN(CF.sub.3SO.sub.3).sub.2, LiBr, or any combinations thereof. A
lithium salt with lower lattice energy can increase the ionic
conductivity of the SPEEK solid electrolyte. Furthermore, the
concentration of the lithium salt in the SPEEK solid electrolyte is
better to be at most 9.4 mmol/g, such as 1.6-4.7 mmol/g. Generally,
the ionic conductivity of the SPEEK solid electrolyte is higher
when the lithium salt's content is higher. However, if the lithium
salt's content is too high, white turbidities will occur in the
SPEEK solid electrolyte, and a film of the SPEEK solid electrolyte
can be uneven. This may be caused by destroying the SPEEK's
crystallinity by the over high lithium salt's content therein.
[0029] According to another embodiment of this invention, the
SPEEK's molecular weight is better to be 10,000-50,000 Da, such as
20,000-30,000 Da. Since SPEEK is a polymeric material, the above
SPEEK's molecular weight can affect the formation condition, such
as drying temperature and drying time, and the mechanical strength,
such as tensile strength, of the SPEEK solid electrolyte.
[0030] According to yet another embodiment, the content of the
polar aprotic solvent is less than 40 wt %. The polar aprotic
solvent can be dimethyl sulfoxide (DMSO), N-methyl pyrrolidinone
(NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), or any
combinations thereof.
Preparation of SPEEK Solid Electrolyte
[0031] The SPEEK solid electrolyte above can be prepared by the
following steps. First, SPEEK can be prepared by sulfonating
polyetheretherketone (PEEK). The sulfonating agent of the
sulfonating reaction above can be sulfuric acid, for example. The
sulfonating condition of the sulfonating reaction above can be
performed at about 50.degree. C. for about 12 hours, for example.
An exemplary chemical structure of the obtained SPEEK is shown
below.
##STR00001##
[0032] Then, a SPEEK solution is prepared by dissolving sulfonated
polyetheretherketone (SPEEK) in a polar aprotic solvent. According
to an embodiment, the SPEEK solution contains 1-12 wt % of SPEEK.
The polar aprotic solvent can be DMSO dimethyl sulfoxide (DMSO),
N-methyl pyrrolidinone (NMP), dimethylformamide (DMF),
dimethylacetamide (DMAc), or any combinations thereof, for
example.
[0033] According to another embodiment, the SPEEK solution can be
further optionally heated to increase the dissolving rate or the
SPEEK in the polar aprotic solvent. For example, if the weight of
the SPEEK solution is about 105 g (5 g SPEEK+100 g DMSO), the SPEEK
solution can be heated at about 60.degree. C. for about 2-4 hours
to substantially dissolve the SPEEK therein.
[0034] Next, a lithium salt is dissolved in the SPEEK solution to
form a SPEEK electrolyte solution. The added amount of the lithium
salt can be at most 2 times of the added SPEEK's weight.
[0035] According to an embodiment, the lithium salt can be directly
added into the SPEEK solution to directly dissolve the lithium salt
therein to form the SPEEK electrolyte solution. During this step,
the solution can be further stirred, heated, or stirred and heated,
to uniformly mix each component in the SPEEK electrolyte solution.
The heating temperature can be about 60.degree. C. to 70% of the
polar aprotic solvent's boiling point. If the heating temperature
is too low, the solubility of the SPEEK in the polar aprotic
solvent will be too low, and the viscosity of the SPEEK electrolyte
solution will be too high to facilitate the subsequent coating
step.
[0036] If the SPEEK electrolyte solution is prepared by a method
including stirring, bubbles may be produced in the SPEEK
electrolyte solution. Since the bubbles will affect the quality of
the SPEEK solid electrolyte, the SPEEK electrolyte solution is
better to stay for a period of time, such as 5-10 minutes, to
remove the bubbles therein.
[0037] Next, the SPEEK electrolyte solution is coated on a
substrate and subsequently dried to form a SPEEK solid electrolyte
layer on the substrate. The substrate above can be a rigid
substrate, such as a stainless steel substrate, or a flexible
substrate, such as a textile.
[0038] The drying temperature and time is usually determined by the
solvent used for the SPEEK electrolyte solution and the needed
solvent content of the finally obtained SPEEK solid electrolyte
layer. Furthermore, the drying temperature and time can affect the
mechanical strength and the ionic conductivity. Accordingly, the
drying temperature above can be about 60-120.degree. C., such as
60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120.degree.
C. The drying time can be at most 72 hours.
[0039] Finally, the dried SPEEK solid electrolyte layer on the
substrate can be further optionally immersed in a lithium salt
solution for about 1-60 sec after the drying step to reduce the
charge transfer resistance between the solid electrolyte and a
contacting electrode, but also increase the mobility of ions in
solid electrolyte. Then, the conductivity of the interface between
the SPEEK solid electrolyte layer and an electrode can be further
improved.
[0040] The lithium salt used in the lithium salt solution can be
LiOH, LiNO.sub.3, Li.sub.2SO.sub.4, LiClO.sub.4,
LiCF.sub.3SO.sub.3, LiN(CF.sub.3SO.sub.3).sub.2, or a combination
thereof. The concentration of the lithium salt in the liquid
solution is better to be at most 10 M.
[0041] The solvent used in the lithium salt solution can be water,
ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl
carbonate (DMC), or propylene carbonate (PC).
Preparation of Flexible Lithium Batteries
Using SPEEK Solid Electrolyte
[0042] In another aspect, a preparation method of flexible lithium
batteries is provided. This preparation method of the flexible
lithium batteries basically utilizes the preparation method of the
SPEEK solid electrolyte to increase the related efficacy of the
flexible lithium batteries.
[0043] After the preparation steps of the SPEEK electrolyte
solution above, the SPEEK electrolyte solution can be respectively
coated on both opposite surfaces of a flexible substrate. The
coating method can be spray coating, knife coating, roller coating,
spinning coating, dip coating, or curtain coating. Next, the SPEEK
coated flexible substrates are dried at a temperature of
60-120.degree. C. for at most 72 hours to obtain SPEEK solid
electrolyte films.
[0044] The flexible substrate above can be a textile, such as a
textile made of glass fibers to increase the mechanical strength of
the composite structure of the flexible substrate uniformly coated
by SPEEK solid electrolyte, and thus the finally obtained flexible
lithium batteries.
[0045] Next, a positive electrode layer and a negative electrode
layer are respectively formed on the two opposite outer surfaces of
the composite structure of the flexible substrate uniformly coated
by SPEEK solid electrolyte to obtain the flexible lithium battery.
For example, the flexible lithium battery can be assembled by the
following method, but this invention is not limited thereto.
[0046] In this method, a positive and a negative electrode layers
can be independently formed by using suitable material. Then, the
composite structure of the flexible substrate embedded in the SPEEK
solid electrolyte film is sandwiched by the positive and the
negative electrode layers. A thermopressing step is performed to
combine each material layer to obtain a flexible lithium battery.
During the thermopressing step, the solvent content of the SPEEK
solid electrolyte layers will be further reduced by
evaporating.
[0047] Moreover, the SPEEK solid electrolyte can be further used to
prepare flexible capacitors. For example, a textile can also be
used as the flexible substrate to obtain a composite structure of
the flexible substrate embedded in the SPEEK solid electrolyte
film. Then, the composite structure above can be used to form a
textile capacitor.
[0048] For better understanding the preparation method and the
properties of the SPPEK-based solid electrolyte, some experimental
results are provided below.
Experiment 1
Effect of Various Lithium Salts to Resistance
[0049] In this experiment, a SPEEK solution was prepared by adding
5 g of SPEEK into 100 g of DMSO, and then stirred at 60.degree. C.
to dissolve the SPEEK in the DMSO. Next, various lithium salts were
respectively added into the SPEEK solution to form various SPEEK
electrolyte solutions with various lithium salts. Each of the SPEEK
electrolyte solutions was then coated on a substrate and then dried
at 60.degree. C. to form SPEEK solid electrolyte on the substrate.
Finally, the SPEEK solid electrolyte on the substrate was immersed
in water for 10 sec. The conditions and results are listed in Table
1.
TABLE-US-00001 TABLE 1 Effect of Various Lithium Salts to
Resistance Samples Lithium salt Resistance (.OMEGA.) 1-1 -- 1.739
1-2 LiClO.sub.4 1.537 1-3 LiCF.sub.3SO.sub.3 1.087 1-4
LiN(CF.sub.3SO.sub.3).sub.2 0.874
[0050] From the result of the Table 1, it can be known that
resistance of the SPEEK solid electrolyte containing
LiN(CF.sub.3SO.sub.3).sub.2 is the smallest. It showed that the
transportation of LiN(CF.sub.3SO.sub.3).sub.2 in the SPEEK solid
electrolyte was the easiest.
Experiment 2
Effect of Lithium Salt Concentration to Ionic Conductivity
[0051] In this experiment, a SPEEK solution was prepared by adding
5 g of SPEEK into 100 g of DMSO, and then stirred at 60.degree. C.
to dissolve the SPEEK in the DMSO. Next, various amounts of
LiClO.sub.4 was added into the SPEEK solution to form SPEEK
electrolyte solutions with various lithium salt concentration. Each
of the SPEEK electrolyte solutions was then coated on a substrate
and then dried at 60.degree. C. to form SPEEK solid electrolyte on
the substrate. Finally, the SPEEK solid electrolyte on the
substrate was immersed in water for 10 sec. The conditions and
results are listed in Table 2.
TABLE-US-00002 TABLE 2 Effect of Lithium Salt Concentration to
Ionic Conductivity Concentration of LiClO.sub.4 Ionic Conductivity*
Sample (mmol/g) (S/cm) 5-1 0 6.21 .times. 10.sup.-3 5-2 1.6 9.40
.times. 10.sup.-3 5-3 2.7 12.63 .times. 10.sup.-3 5-4 3.5 16.04
.times. 10.sup.-3 *Ionic Conductivity = thickness/(resistance
.times. surface area), wherein resistance was measured by AC
impedance analyzer including Potentiostat/Galvanostat (Model 263 A)
and Frequency Response Detector (Model FRD100) purchased from
Princeton Applied Research.
[0052] From the results of Table 2, it can be known that the ionic
conductivity was increased with the increase of the lithium salt
content.
Experiment 3
Thermal Change Rate of Conductivity and Capacitance of
LiClO.sub.4-SPEEK Solid Electrolyte
[0053] In Examples 3-1 to 3-3 of this experiment, a SPEEK solution
was prepared by adding 5 g of SPEEK into 100 g of DMSO, and then
stirred at 60.degree. C. to dissolve the SPEEK in the DMSO. Next,
LiClO.sub.4 was added into the SPEEK solution to form SPEEK
electrolyte solutions. Each of the SPEEK electrolyte solutions was
then coated on a substrate and then dried at 60.degree. C. to form
SPEEK solid electrolyte on the substrate. The concentration of the
LiClO.sub.4 in the SPEEK solid electrolyte is 4.7 mmol/g. Next,
each of the SPEEK solid electrolytes was immersed in various
immersing liquids for about 10 seconds, and then respectively
measured the conductivity and the capacitance at 25.degree. C. and
80.degree. C.
[0054] In Comparative Examples 3-1 and 3-2, poly vinyl alcohol
(PVA) and polyethylene oxide (PEO) were used to replace SPEEK to
prepare PVA solid electrolyte and PEO solid electrolyte. The
concentration of the LiClO.sub.4 in the PVA solid electrolyte was
3.2 mmol/g. The concentration of the LiClO.sub.4 in the PEO solid
electrolyte was unknown, since Choi's paper did not disclose it.
The conductivity and the capacitance of the Comparative Examples
were respectively measured at 25.degree. C. and 80.degree. C.
[0055] The preparation conditions and results are listed in Table
3.
TABLE-US-00003 TABLE 3 Thermal Change Rate of Conductivity and
Capacitance of LiClO.sub.4-SPEEK solid electrolyte Polymer-Based
Thermal Change Rate (%) Solid Immersing over 25-80.degree. C.
Electrolyte Liquid .sup.1Conductivity .sup.2Capacitance Example 3-1
SPEEK-LiClO.sub.4 Water 77.9 38.7 Example 3-2 3M 27.2 55.3
LiON.sub.(aq) Example 3-3 3M 15.0 16.4 LiNO.sub.3(aq) Comparative
PVA-LiClO.sub.4 Water 429.5 334.1 Example 3-1 Comparative
.sup.3PEO-LiClO.sub.4 -- 32,400 -- Example 3-2 .sup.1Calculated by
(.sigma..sub.80.degree. C. - .sigma..sub.25.degree.
C.)/.sigma..sub.25.degree. C. .times. 100 .sup.2Calculated by
(C.sub.80.degree. C. - C.sub.25.degree. C.)/C.sub.25.degree. C.
.times. 100 .sup.3From FIG. 2 of Materials Science and Engineering,
B107 (2004), pp 244-250.
[0056] From the results of Table 3, it can be known that the
thermal change rate of the conductivity and capacitance for the
SPEEK solid electrolytes is the smallest among the three different
kinds of polymers (SPEEK, PVA, and PEO). In Examples 6-1 to 6-3,
the various immersing liquids also affect the thermal change rate
of the conductivity and capacitance. The most amazing one is
SPEEK-LiClO.sub.4 immersed in LiNO.sub.3(aq), which has only a
thermal change rate of 15.0% for conductivity and 16.4% for
capacitance.
Experiment 4
Thermal Change Rate of Conductivity and Capacitance of
LiCF.sub.3SO.sub.3-SPEEK Solid Electrolyte
[0057] In Examples 4-1 to 4-3, a SPEEK solution was prepared by
adding 5 g of SPEEK into 100 g of DMSO, and then stirred at
60.degree. C. to dissolve the SPEEK in the DMSO. Next,
LiCF.sub.3SO.sub.3 was added into the SPEEK solution to form SPEEK
electrolyte solutions. Each of the SPEEK electrolyte solutions was
then coated on a substrate and then dried at 60.degree. C. to form
SPEEK solid electrolyte on the substrate. The concentration of the
LiCF.sub.3SO.sub.3 in the SPEEK solid electrolyte was 3.2 mmol/g.
Next, each of the SPEEK solid electrolytes was immersed in various
immersing liquids for about 10 seconds, and then respectively
measured the conductivity and the capacitance at 25.degree. C. and
80.degree. C. The preparation conditions and results are listed in
Table 4.
TABLE-US-00004 TABLE 4 Thermal Change Rate of Conductivity and
Capacitance of LiCF.sub.3SO.sub.3-SPEEK solid electrolyte Thermal
Change Rate (%) over 25-80.degree. C. Examples Immersing Liquid
.sup.1Conductivity .sup.2Capacitance 4-1 Water 101.3 341.6 4-2 3M
LiOH.sub.(aq) 55.7 107.1 4-3 3M LiNO.sub.3(aq) 2.0 39.2
.sup.1Calculated by (.sigma..sub.80.degree. C. -
.sigma..sub.25.degree. C.)/.sigma..sub.25.degree. C. .times. 100
.sup.2Calculated by (C.sub.80.degree. C. - C.sub.25.degree.
C.)/C.sub.25.degree. C. .times. 100
[0058] From the results of Table 4, it can be known that the SPEEK
solid electrolyte having the smallest thermal change rate was still
the one (Sample 4.3) immersed in LiNO.sub.3 solution after the
lithium salt in SPEEK solid electrolyte was changed from
LiClO.sub.4 to LiCF.sub.3SO.sub.3.
[0059] The inventors discovered that the LiCF.sub.3SO.sub.3-SPEEK
solid electrolyte would undergo oxidation reaction when the
operation voltage greater than 0.5 V, and the capacitance
calculated from cyclic voltammetry curve was thus increased. This
may be the reason why the thermal change rate is so great for the
LiCF.sub.3SO.sub.3-SPEEK solid electrolyte of Sample 4-1 immersed
in water. However, LiCF.sub.3SO.sub.3-SPEEK solid electrolytes of
Samples 4-2 and 4-3 immersed in lithium solution can effectively
inhibit the oxidation reaction to decrease the thermal change rate
of conductivity and capacitance of the LiCF.sub.3SO.sub.3-SPEEK
solid electrolytes to increase the thermal stability thereof.
Experiment 5
Thermal Change Rate of Conductivity and Capacitance of
LiN(CF.sub.3SO.sub.3).sub.2-SPEEK Solid Electrolyte
[0060] In Examples 5-1 to 5-3, a SPEEK solution was prepared by
adding 5 g of SPEEK into 100 g of DMSO, and then stirred at
60.degree. C. to dissolve the SPEEK in the DMSO. Next,
LiN(CF.sub.3SO.sub.3).sub.2 was added into the SPEEK solution to
form SPEEK electrolyte solutions. Each of the SPEEK electrolyte
solutions was then coated on a substrate and then dried at
60.degree. C. to form SPEEK solid electrolyte on the substrate. The
concentration of the LiN(CF.sub.3SO.sub.3).sub.2 in the SPEEK solid
electrolyte was 1.6 mmol/g. Next, each of the SPEEK solid
electrolytes was immersed in various immersing liquids for about 10
seconds, and then respectively measured the conductivity and the
capacitance at 25.degree. C. and 80.degree. C. The preparation
conditions and results are listed in Table 5.
TABLE-US-00005 TABLE 5 Thermal Change Rate of Conductivity and
Capacitance of LiN(CF.sub.3SO.sub.3).sub.2-SPEEK solid electrolyte
Thermal Change Rate (%) over 25-80.degree. C. Examples Immersing
Liquid .sup.1Conductivity .sup.2Capacitance 5-1 Water 94.7 755.7
5-2 3M LiOH.sub.(aq) 13.6 57.9 5-3 3M LiNO.sub.3(aq) 26.6 57.3
.sup.1Calculated by (.sigma..sub.80.degree. C. -
.sigma..sub.25.degree. C.)/.sigma..sub.25.degree. C. .times. 100
.sup.2Calculated by (C.sub.80.degree. C. - C.sub.25.degree.
C.)/C.sub.25.degree. C. .times. 100
[0061] From the results of Table 5, it can be known that the
thermal change rate of conductivity and capacitance of the SPEEK
solid electrolyte were similar for the Samples 5-2 and 5-3 immersed
in LiNO.sub.3 and LiOH solution, after the lithium salt in SPEEK
solid electrolyte was changed from LiClO.sub.4 to
LiN(CF.sub.3SO.sub.3).sub.2. SPEEK solid electrolyte immersed in
LiOH solution (Sample 5-2) was still better.
[0062] The inventors discovered that the
LiN(CF.sub.3SO.sub.3).sub.2-SPEEK solid electrolyte would undergo
oxidation reaction when the operation voltage greater than 0.5 V,
and the capacitance calculated from cyclic voltammetry curve was
thus increased. This may be the reason why the thermal change rate
is so great for the LiN(CF.sub.3SO.sub.3).sub.2-SPEEK solid
electrolyte of Sample 5-1 immersed in water. However,
LiN(CF.sub.3SO.sub.3).sub.2-SPEEK solid electrolytes of Samples 5-2
and 5-3 immersed in lithium solution can effectively inhibit the
oxidation reaction to decrease the thermal change rate of
conductivity and capacitance of the
LiN(CF.sub.3SO.sub.3).sub.2-SPEEK solid electrolytes to increase
the thermal stability thereof.
Experiment 6
Thermal Change Rate of Conductivity of SPEEK Solid Electrolytes
[0063] The preparation methods for each sample of SPEEK solid
electrolytes containing lithium salts have been described above,
and thus omitted here. The preparation method for sample of SPEEK
solid electrolyte without containing lithium salts was basically
the same as those preparation methods for PEEK solid electrolytes
containing lithium salts, except the lithium salt adding step was
omitted. The results are listed in Table 6 below.
TABLE-US-00006 TABLE 6 Thermal Change Rate of Conductivity* of
SPEEK solid electrolytes Lithium salt of SPEEK Immersing Liquid
solid electrolyte 3M LiOH.sub.(aq) 3M LiNO.sub.3(aq) -- -59.2 170.5
LiClO.sub.4 27.2 15.0 LiCF.sub.3SO.sub.3 55.7 2.0
LiN(CF.sub.3SO.sub.3).sub.2 13.6 26.6 *Calculated by
(.sigma..sub.80.degree. C. - .sigma..sub.25.degree.
C.)/.sigma..sub.25.degree. C. .times. 100
[0064] From the results of Table 6, it can be known that there were
two factors could affect the thermal change rate of the
conductivity and capacitance. One was the kinds of the lithium salt
in the immersing liquid, and the other was the kinds of the lithium
salt in the SPEEK solid electrolyte. In Table 6, the thermal change
rate of the conductivity of the SPEEK solid electrolyte without
adding lithium salt was the largest, and it shows that the thermal
stability of the SPEEK solid electrolyte without adding lithium
salt was poor. Among SPEEK solid electrolytes containing lithium
salts, the LiCF.sub.3SO.sub.3-SPEEK solid electrolyte immersed in
LiNO.sub.3 solution had the smallest thermal change rate, only 2%,
very surprisingly. The thermal change rate of conductivity of the
other SPEEK solid electrolytes containing lithium salts were all
below 56%.
[0065] In light of foregoing, the SPEEK solid electrolyte
containing lithium salts can have excellent thermal stability. This
result shows that SPEEK solid electrolytes are very suitable to be
used in various electronic products requiring to be operated under
high temperature. For example, lithium batteries and flexible
supercapacitors containing the SPEEK solid electrolytes above can
be used in the electronic products of cars.
[0066] All the features disclosed in this specification (including
any accompanying claims, abstract, and drawings) may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, each feature
disclosed is one example only of a generic series of equivalent or
similar features.
* * * * *